<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style type="text/css" rel="stylesheet">
        a{
            color: red;
            font-size: 50px;
        }
        .aa{
            background-color: blue;
            font-size: 100px;
        }
        #a4{
            font-weight: bold;
        }
    </style>
</head>
<body>
<a class="aa">连接2</a>
<a class="aa">连接3</a>
<a id="a4">连接4</a>
</body>
</html>